走离效应对级联和频与差频波长转换的影响

Wavelength conversion based on cascaded SFG+DFG in pulsed pumping

通过理论分析和数值模拟研究了在双脉冲泵浦情况下的级联和频与差频的二阶非线性效应,探讨了走离效应对波长转换的影响。由于不同波段的光脉冲之间的群速度失配导致光脉冲之间的走离,使和频光脉冲随波导长度不断产生并展宽,结果表明在走离效应的影响下和频光脉冲移出非线性效应作用区带走能量,作用区的能量平衡关系被破坏;差频转换效率受到和频转换效率较低的遗传而下降;同时转换脉冲波形受到和频脉冲展宽的影响而发生了畸变。研究还表明,双泵浦波长同时变动时泵浦带宽很宽,而单一泵浦波长变动时泵浦带宽很窄。

The cascaded second-order nonlinear interactions of Sum-frequency and Difference-frequency Generation （SFG＋DFG） in periodically poled lithium niobate waveguide were presented. Through theoretical analysis and numerical simulations, the walk-off effect between sum-frequency pulse and pump pulse caused by Group Velocity Mismatch （GVM） was discussed. The results demonstrate that Sum Frequency （SF） pulse is continually broadened with wavelength and scatters the energy from the interaction zone in pulsed pumping wavelength conversion, so the balance of energy in the center of interactions is broken. As a result, the conversion efficiency of Difference Frequency （DF） greatly increases because of the low conversion efficiency of SF and DF pulse waveform is asymmetrical with a phase shift of peak power At the same time, the results demonstrate that the pump-bandwidth is broad if two pump-wavelengths are adjusted simultaneously and it is narrow if only one pump-wavelength is adjusted alone